The Horse and His Boy by C.S. Lewis, was the fifth to be published in The Chronicles of Narnia series. The story is set in the period covered by the last chapter of The Lion, the Witch, and the Wardrobe during the reign of the four children as monarchs of Narnia. The main characters are two children and two talking horses who escape from Calormen and travel north into Narnia. On their journey, they learn of the Prince of Calormen's plan to invade Archenland, and warn the King of Archenland of the impending attack. The lion Aslan appears in the story to demonstrate the idea of divine providence.